Differences Between AOD and VOD Stainless Steel Making Processes

Differences Between AOD and VOD Stainless Steel Making Processes

AOD Process (Argon-Oxygen Decarburization)

In the AOD process, initial melting is carried out in a conventional furnace. The molten metal is then transferred to an AOD converter, where refining is performed through controlled redox reactions. A mixture of argon and oxygen is blown into the melt through tuyeres (nozzles), ensuring continuous stirring of the bath.

The injection of argon and oxygen not only promotes mixing but also supports exothermic reactions that raise the temperature to approximately 1650°C. The primary reaction is decarburization, during which excess carbon combines with oxygen to form carbon monoxide, enabling carbon levels to be reduced to as low as 0.015%. The oxidation loss of chromium is minimized by carefully calibrated ratios of oxygen to argon. Once the target chemical composition is achieved, the steel is cast either continuously or into ingot molds.

VOD Process (Vacuum Oxygen Decarburization)

The initial melting stage in VOD is similar to that of AOD. The key difference is that the molten steel is poured into a ladle, which is then placed inside a vacuum chamber. The chamber is evacuated to an initial pressure of about 3 mbar and stabilized near 0.6 mbar. The vacuum environment enhances decarburization while preventing excessive oxidation of chromium.

Argon is introduced through porous plugs at the ladle bottom to agitate and "wash" the steel. Oxygen is top-blown into the melt via a lance, spreading across the surface and accelerating the formation of carbon monoxide. This enables carbon reduction to levels around 0.015%. Once the target carbon content is reached, adjustments are made to other elements, such as chromium.

Since the decarburization reaction itself generates significant heat, the VOD process requires relatively little external energy to maintain high temperatures. After refining, the steel is tapped and cast into molds.

Summary

Both processes effectively decarburize stainless steel while preserving chromium, but they differ in their operating environments and stirring methods: AOD uses atmospheric pressure with gas injection through tuyeres, while VOD operates under vacuum with combined top oxygen blowing and bottom argon stirring.

 We are a professional electric furnace manufacturer. For further inquiries, or if you require submerged arc furnaces, electric arc furnaces, ladle refining furnaces, or other melting equipment, please do not hesitate to contact us at  susan@aeaxa.com